<html>
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style>
		.parent{
			padding: 10px;
			border: solid 1px #ddd;
			width: 300px;
		}
		.box{
			border: dashed 1px #f00;
			padding: 20px;
			margin-bottom: 5px
		}
		.box1{
			position:relative;
			top:-20px;
			background-color: #f88;
		}
		.box2{
			background-color: #f00;
		}
		.box3{
			background-color: #0f8;
		}
	</style>
</head>
<body>
	<div class="parent">
		<div class="box box1">第一个盒子</div>
		<div class="box box2">第二个盒子</div>
		<div class="box box3">第三个盒子</div>
	</div>
</body>
</html>